German Patent No. 35 06 118 describes a bus system for the transmission of messages which is also referred to as a CAN bus. With the CAN bus, high-priority messages are transmitted preferentially. For this, each message is preceded by a so-called "header," which decides which message is to be transmitted next when the bus is free. It is not possible, however, to interrupt a message in progress. Furthermore, all messages have the same amplitude between high and low bit states.
In "Bus Contention and Overload Detecting Transmitter," IBM Technical Disclosure Bulletin, Vol. 34, No. 8, Jan. 1, 1992, pp. 10-13, a bus system is described in which messages can be aborted by overwriting bits. Higher-priority messages can then gain access to the bus in a new arbitration subsequent thereto.